The present invention relates to an operating method for a grinding body mill, such as for example a stirred ball mill and to a grinding body mill for carrying out said operating method.
A stirred ball mill known from practice, which is an example of a grinding body mill 1 in general and which is schematically illustrated in FIG. 2 in a sectional view, comprises a grinding chamber 3 which is surrounded by a housing 2 and into which grinding stock 5 to be milled is fed through a product inlet 4. In the grinding chamber 3 there are contained grinding bodies 6 and an agitator 7 with a rotor 8, the rotation of which serves to generate the intensive movement of the grinding bodies 6, whereby the grinding stock 5 to be milled is milled. On the axial end of the rotor 8 there is situated an in particular co-rotating separating device 9 serving for separation between grinding bodies 6 and grinding stock 5 that has still to be milled, on the one hand, as well as fully ground grinding stock 10, on the other hand, and being positioned upstream of a product outlet 11 in the housing 2.
The separating device 9 is formed for example by a bladed rotor body 12 which rotates together with the rotor 8 and which is designed and operated with the intention of preventing grinding bodies 6 from passing through it, by virtue of the separating device 9, in particular by way of the size of the intermediate spaces between the blades 13 of the bladed rotor body 12 and the rotational movement of the bladed rotor body 12, deflecting the grinding bodies 6 and thus preventing them from passing through the separating device 9 from the grinding chamber 3 into the product outlet 11. Whereas, during normal operation of the mill, the rotation of the separating device 9 alone ensures that grinding bodies 6 are reliably predominantly prevented from passing through the separating device 9 and exiting the grinding body mill 1 or the grinding chamber 3 thereof through the product outlet 11, it is the case in particular in braking phases of the rotor 8 that, owing to the relatively low rotational speed of the rotor 8 and thus of the bladed rotor body 12 of the separating device 9, individual grinding bodies 6 pass through the latter from the grinding chamber 3 into the product outlet 11. This may however also occur during normal operation if the dimensions of grinding bodies 6 have decreased as a result of wear.
Such grinding bodies that have escaped from the grinding chamber 3 must, on the one hand, separately be removed from the fully ground grinding stock 10, specifically as far as possible without impeding a continuous flow of grinding stock. To maintain a predefined quantity of grinding bodies in the grinding chamber 3 despite resulting grinding body losses, it is, on the other hand, also necessary to repeatedly perform replenishment of grinding bodies, for which purpose cumbersome determinations and monitoring of the corresponding quantity of grinding bodies are necessary. All of this entails additional outlay for the operation of a grinding body mill.
The recirculation of grinding bodies is disclosed in DE 27 44 802 A1 and in US 2 332 01 A, albeit with considerable outlay.
DE 24 46 341 A1 and DE 31 31 370 A1 are concerned generally with stirred ball mills. All of said mills lack a co-rotating separating device upstream of a product outlet.